The present invention relates to acid sanitizing and/or cleaning compositions comprising antimicrobially effective C5 to C4 carboxylic acids. The present invention is directed to both concentrates and to water diluted use solutions.
Periodic cleaning and sanitizing in food, drink, pharmaceutical, cosmetic and similar processing industries; in food preparation and service businesses; in health and day care facilities; and, in hospitality establishments are a necessary practice for product quality and public health. Residuals left on equipment surfaces or contaminants found in the process or service environment can harbor and nourish growth of subsequent processed product or critical contact surfaces. Protecting the consumer against potential health hazards associated with pathogens or toxins and maintaining the quality of the product or service requires routine cleaning of residuals from surfaces and effective sanitation to reduce microbial populations.
Visual inspection of the equipment cannot ensure that surfaces are clean or free of microorganisms. Antimicrobial treatments as well as cleaning treatments are therefore required for all critical surfaces in order to reduce microbial population to safe levels established by public health regulations. This process is generally referred to as sanitizing. The practice is of sanitation is particularly of concern in food process facilities wherein the cleaning treatment is followed by an antimicrobial treatment applied upon all critical surfaces and environmental surfaces to reduce the microbial population to safe levels established by ordinance. A sanitized surface is, as defined by the Environmental Protection Agency (EPA), a consequence of a process or program containing both an initial cleaning and a subsequent sanitizing treatment which must be separated by a potable water rinse. A sanitizing treatment applied to a cleaned food contact surface must result in a reduction in population of at least 99.999% (5 log) for specified microorganisms as defined by the xe2x80x9cGermicidal and Detergent Sanitizing Action of Disinfectantsxe2x80x9d, Official Methods of Analysis of the Association of Official Analytical Chemists, paragraph 960.09 and applicable sections, 15th Edition, 1990 (EPA Guideline 91-1).
The antimicrobial efficacy of sanitizing treatments is significantly reduced if the surface is not absolutely free of soil and other contaminants prior to the sanitizing step. The presence of residual food soil and/or mineral deposits inhibit sanitizing treatments by acting as physical barriers which shield microorganisms lying within the organic or inorganic layer from the microbicide. Furthermore, chemical interactions between the microbicide and certain contaminants can disrupt the killing mechanism of the microbicide.
With the advent of automated clean-in-place and sanitize-in-place systems, the need for disassembly has been diminished, and cleaning and sanitizing have become much more effective. However, modern food industries still rely on sanitizers to compensate for design deficiencies or operational limitations in their cleaning programs and the probability of very small residual amounts of organic and inorganic soils and biofilms remaining on food contact surfaces after cleaning. In cooperation with these process changes and higher performance expectations, sanitizer treatments must also comply with the increasing demand for safer, less corrosive, more environmentally friendly compositions.
According to the U.S. Center for Disease Control and Prevention, food poisoning in calendar year 2000 resulted in 5000 deaths, 325,000 hospitalizations and 76,000,000 illnesses. The need exists for improved sanitizing treatments to destroy pathogens and food spoilage microorganisms resistant to conventional treatments within the food gathering, food processing, and food serving industries. A further complication is that the list of approved microbicidal agents has continued to decrease due to acute and chronic human toxicity of some microbicidal agents, and to their environmental persistence in water supplies.
Antimicrobially active acids have been used in sanitizing operations. For instance, U.S. Pat. No 404,040 describes a sanitizing composition comprising aliphatic, short chain fatty acids, a hydrotrope or solubilizer for the fatty acids, and a hydrotrope-compatible acid, and U.S. Pat. No. 5,330,769 describes fatty acid sanitizer concentrates and diluted final solutions which include individual amounts of germicidally effective fatty acid, hydrotrope, a strong acid group consisting of phosphoric acid and sulfuric acid or mixtures thereof sufficient to lower the pH of the final solutions to about 1-5, and a concentrate stabilizing weak acid component selected from the group consisting of propionic, butyric and valeric acids and mixtures thereof.
Protonated carboxylic acids offer broad spectrum antimicrobial activity against gram-positive and gram negative bacteria, persistent biocidal activity in the presence of organic and inorganic soils and residual biocidal and inhibitory activity. They combine both acid for mineral deposit control and sanitizer for antimicrobial effect into one treatment solution.
However, one problem associated with the use of protonated carboxylic acid sanitizers is poor use dilution phase stability, particularly at lower water temperatures of 40xc2x0-50xc2x0 F. 50xc2x0 F. Fatty monocarboxylic acids having alkyl chains containing 5 or more carbon atoms, are typically characterized as water insoluble and can oil out or precipitate from solution as a gelatinous flocculent. Solubility tends to decrease with decreasing water temperature and increasing ionic concentration. Furthermore, the oil or precipitate can affix to the very surfaces which the sanitizing solution is intended to sanitize, such as equipment surfaces, leading to a film formation on these surfaces over time. The fatty acid film deposited and left remaining on the equipment surface tends to have a higher pH than the sanitizing solution from which it came resulting in a significantly lowered biocidal efficacy, and, if mixed with food soil, may result in a film matrix which has the potential of harboring bacteria, an effect opposite to that desired.
One solution has been to use short chain, C1-C4 carboxylic or hydroxycarboxylic acids to solubilize and thus stabilize longer chain fatty acids in high actives composition concentrates. However, these short chain weak acids have been known to be less effective at normal use dilution concentrations than their longer chain counterparts, and extreme dilution of the concentrate in water leads to a decrease in the solvating effect resulting in a precipitate of the longer chain length fatty acids of C5 or higher from solution. Furthermore, raising the concentration of the C1-C4 acids increases the cost of the sanitizing composition, and does not appear to result in a significant increase in dilution stability or to improved antimicrobial efficacy.
Organic hydrotropes or coupling agents, such as low molecular weight sulfonates, may be employed to increase the solubility and miscibility of the longer chain fatty acids with water and inorganic salts both in concentrated and in diluted use solutions. Again, the solubility appears to diminish at sustained lower water temperatures with the result being phase separation.
There remains a need in the art for an improved biocidal composition which utilizes a carboxylic fatty acid which has high antimicrobial efficacy, has good phase stability, exhibits low toxicity, and is not detrimental to the environment.
Surprisingly, the compositions of the present invention exhibit excellent phase stability both in concentrated form and in diluted use solutions, and in particular, they exhibit excellent phase stability in low temperature water diluted use solutions. Even more surprisingly, the stability is improved in the presence of nitric acid.
The sanitizing and/or cleaning compositions of the present invention, in both concentrated and in diluted use solutions, include an antimicrobially effective short chain fatty acid, a shorter chain weak carboxylic acid, and a strong mineral acid. The shorter chain weak carboxylic acid functions as a solvent.
The shorter chain weak carboxylic acid functions as a solvent for the antimicrobial short chain fatty acid. In concentrated form, the compositions also desirably contain an organic hydrotrope.
In some embodiments, the antimicrobially effective short chain fatty acid is a C5 to C14 fatty acid, and more suitably C6 to C10 fatty acid, or some mixture thereof, the shorter chain weak carboxylic acid is a C1 to C4 carboxylic acid, and the strong mineral acid is nitric, or a mixture of nitric and phosphoric acids.
In some embodiments wherein a hydrotrope is included in the composition, an anionic sulfonate hydrotrope is employed.
Additionally, the composition may optionally include at least one anionic and/or nonionic surfactant. In some embodiments, a nonionic surfactant is suitably employed to improve surface wetting, soil removal, and so forth. It may also function to improve the solubility of the fatty acids at use dilutions.
The antimicrobailly effective effective short chain fatty acid is useful from about 3 wt-% to about 12 wt-% of the concentrate, and more suitably from about 5 wt-% to about 10 wt-% of the concentrate. In one particular embodiment, the concentrate includes a blend of two fatty acids.
The weak carboxylic acid is useful from about 5 wt-% to about 50 wt-% of the concentrate, and more suitably from about 10 wt-% to about 40 wt-% of the concentrate. In one particular embodiment, the weak carboxylic acid component includes at least acetic acid. The weak carboxylic acid acts as a solvent for the antimicrobially active short chain fatty acid.
The strong mineral acid is useful from about 5 wt-% to about 50 wt-% of the concentrate, and more suitably about 15 wt-% to about 40 wt-% of the concentrate. In some embodiments, the strong mineral acid is nitric which is useful from about 5 wt-% to about 50 wt-% of the concentrate, and more suita concentrate. If phosphoric acid is employed, it is useful from 5 wt-% to about 40 wt-% of the concentrate, and more suitably about 10 wt-% to about 35 wt-% of the concentrate.
Surprisingly, the antimicrobially active short chain fatty acid is stable in nitric acid.
The compositions may further comprise optional ingredients including urea for stabilization of nitric acid, and a surfactant component. The surfactant component may include one or more surfactants. In some embodiments, an anionic or nonionic surfactant may be optionally added at a level of 0.1 wt-% to about 50 wt-% of the concentrate, more suitably about 0.25 wt-% to about 40 wt-% of the concentrate, even more suitably about 0.5 wt-% to about 40 wt-%, and most suitably about 1 wt-% to about 30 wt-%.
In some embodiments, an anionic hydrotrope is employed at a level of about 0.5 wt-% to about 50 wt-%, suitably about 1 wt-% to about 40 wt-% of the concentrate, and more suitably from about 5 wt-% to about 30 wt-% of the concentrate. In one embodiment, the anionic hydrotrope includes at least one alkylsulfonate.
The compositions may be diluted with water at any ratio whatsoever, but typically the ratio is between about 1:100 parts of the concentrate to water to about 1:1500 parts of the concentrate to water. This is referred to as a use dilution. A very typical use dilution is about 1 ounce of concentrate to about 6 gallons of water which is a ratio of about 1:768 parts of the concentrate to water.
The compositions of the present invention find utility as both sanitizing and disinfecting compositions as well as cleaning compositions, and are useful for both hard and soft surface sanitizing and disinfecting in farm operations, food processing operations, institutional food preparation and serving areas, health care and child care facilities as well as any other number of contact sensitive environments. The compositions exhibit high antimicrobial efficacy while having low toxicity, are not detrimental to the environment, and do not contaminate food stuffs.
The compositions also find utility for use as one-step cleaning/sanitizing compositions and disinfectants in which the composition cleans and sanitizes simultaneously.